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Tuesday, March 6, 2018

Baleen Whale Sub-Species Found To Feed While Treading Water

University of Tokyo scientists have discovered that the Bryde’s whale, a type of baleen whale that usually feeds by lunge feeding, will actually perform passive feeding as well, modifying its feeding strategy according to its environment.

Yeah… just like you might dine in with your elbows on the TV table bereft of pants while eating a couple of Hungry Man dinners (one of those suckers will never fill up a real man) alone at home—but when your feeding environment changes and you have a date (how did that happen?), you will suddenly become the living embodiment of manners and style, a regular Bond. James Bond of dining etiquette.

The university researchers noted that when a Bryde's whale is foraging for food in the shallows waters - in this case in the upper Gulf of Thailand in Southeast Asia - because the waters in that area are lacking in oxygen except at the sea surface thanks to excessive nutrients caused by an outflow of fresh water from rivers (and the sewage contained within)—the small fish the whale prefers to consume are usually close to the water’s surface.

Visually, this is like you and me floating upright in the water, with our lower jaw only in the water, with the rest of our mouth open…

The research group led by then-post graduate researcher for ocean science Iwata Takashi (surname first) at the Atmosphere and Ocean Research Institute at the University of Tokyo discovered through visual observations and information gathered using data loggers attached to the animals, that Bryde's whales will passive feed at the surface by treading water and opening their mouth until the lower jaw contacts the sea surface, waiting for the prey to enter.

Bryde's whale passive tread-water feeding. Image © 2018 Takashi Iwata.
The energy cost of this tread-water feeding, considered passive feeding behavior, is much lower than that for lunge feeding, which involves active chasing and engulfing with an open mouth at high speeds to capture a large amount of prey in deeper waters.
Computer image representation of a Bryde's whale lunge feeding. 
What it means, is that it does not expend as much energy to feed, ergo it doesn’t need to feed as much, preserving more of its food source for later.

Or, in the case of the Bryde's whales feeding in the waters off Thailand, there's less chance of all that sewage entering its mouth.

As someone who has sucked on a plastic tube to start a vacuum when cleaning out my 40-gallon aquarium that is filled with fish pee and poop, and I can tell you that a Bryde's whale has no interest in getting anything that bad into its maw - Bleech!  

The research team saw the behavior in solitary whales as well as with adult-calf pairs, which implies that the behavior is learned.

While this passive feeding technique has only so fare been observed in this part of the Gulf of Thailand and with these whales, this could simply be a group’s learned social behavior to accommodate the polluted areas where it feeds.

In other words, the Bryde’s whale is learning, and therefore does what it does to survive.

I know… no big whoop to most of you dear readers, but I find it fascinating to see observable evidence of creatures learning how to adapt when man throws crap balls at it.

For me it is further evidence that when left to their own devices, nature finds a way. Sometimes.

In Japan, early whalers called the Bryde's whale the the anchovy (鰯, iwashi) or skipjack whale (鰹鯨, katsuo-kujira), as it feeds on anchovy and it was commonly associated with the skipjack tuna.

Later when modern whaling shifted to the Sanriku area, Japanese whalers confused it with the similar-looking sei whale, which (sei whale) then became known as the iwashi-kujira (鰯鯨, anchovy whale). Incidentally, anchovies are dominant prey for both species off Japan.

The Bryde's whales are now called nitari-kujira (似鯨, "look-alike whale") in Japan, for their resemblance to the sei whale. They should just call it a Bryde's whale. 

Depending on the particular form of the Bryde's whale (there are apparently three versions), its size range of adults can range from as small as 11.9 meters (39-feet) up to 15.51 meters (50.9 feet), with a weight of anywhere between 12 to 25 metric tons (13-28 short tons).  

It has twin blowholes with a low splashguard to the front. It has no teeth, but has two rows of baleen plates.

Baleen is a filter-feeder system whereby a baleen-whale opens its mouth underwater to feed, taking in water. The whale then pushes the water out through the baleen plates while the food source such as krill, or in the case of the Bryde's whale - anchovies et al remain in the whale's mouth to be consumed as food.

The Japanese hunt this species as part of their scientific whaling program, having taken some 500 since 2009.

I don't know WHY you need to kill/cull 500 whales as part of one's scientific research... obviously the research group mentioned in this article is NOT killing them...

That 500 killed in the name of research is, in my opinion, bullcrap. and is more than likely a way for Japan to do some whaling that it is not allowed to do.

Still, it is estimated that some 90,000 to 100,000 Bryde's whale still exist, with most living in the Northern hemisphere. 

Andrew Joseph

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